If you’ve found that your Hibernate option is missing from Windows Vista, it might be from running the disk cleanup wizard and removing the hibernate files. This is due to a known bug in Vista that might not have been hotfixed already.

Turning it back on is very simple, however.

Type cmd into the start menu search box, and use Ctrl+Shift+Enter to open in administrator mode. You can also right-click the item in the menu and choose Run as Administrator.

From the command prompt, type in the following command:

powercfg /hibernate on

You’ll have to restart your computer before it will take effect.

Update: Alternative Method

An alternative method with more steps was suggested by Shane in the comments. If the above doesn’t fix your problem, you can use these steps.

Go to the command prompt icon in the Start menu under Accessories and right click the icon: click “Run as administrator”.

Paste: “powercfg.exe /hibernate on” and hit Enter and also paste “powercfg -h on” and hit enter just to be safe.